Railway track insulation breakdown signaling system



July 22, 1947. R. R. KEMMERER ET AL 2,424,319

RAILWAY TRACK INSULATION BREAKDOWN SIGNALING SYSTEM Filed Oct. 7, 1944 4 ,/5 1; I ig-g 127' .4 15 2 p5 Aesonanf 2/ W 12.5 Eeoflflrfiizf 1% [ZEU THE/R ATTORNEY Patented July 22, 1947 RAILWAY TRACK INSULATION BREAK- DOWN: SIGNALING SYSTEM Ralph .R.1Kemmerer, Swissvale, and'Arthur L. Jerome, Edgewood, Pa., assignors to The Union Switch & Signal Company, SwissvalejPa a corporation of Pennsylvania Application October 7, 1944,.Serial No. 557,630

9 Claims. :1

Our invention relates .to railway traffic controlling apparatus and particularlyto a system employing coded energy in the track circuits thereof.

In Letters Patent of the United States No.

2,357,236 of Howard A. Thompson, there isshown a signaling system arrangedso that, ifenergy feeds across the insulated joints separating two track sections, the equipment associated with the track section in advance of the defective joint operates to maintain the wayside sign-a1 for that section at stop and to supply energy of '75 code frequency to the section in the rear of the defective joints to cause the signal forthat section to display its most restrictive proceedvindication. Thesystem of the Thompson patent operates so that after feeding of energy across the joints ceases the signalis'held at stop and energy of '75 code frequency is supplied to the section in the rear until the equipment is reset manually by a maintainer-or other person, or until a train passes through the stretch.

Energy may temporarily feed between two sections when the insulated joints-are not defective. This supply of energy between two sections may result from tools or similar objects placed onthe track by work-men, itmaybecausedby an uninsulated car bridging a joint, or it mayresult from other causes. Under these circumstances it is desirable 'that'as long as energy feeds between the two sections the'signal for the section in advance be held at stop andthat energy of 75 code frequency be supplied to the section in the rear, butin order not to unnecessarily delay trafiic it is desirable to permit the, signal to display a permissive indication and to supply energy of a higher code frequency .to the section in the rear when feeding ofenergy'between the two sections ceases.

-An object of thisinventionis to provide-anv improved system-of the type described which is arranged sothat after feeding of energy between two sections has-been detected and the signal for the forward sect-ion putto stop and energy of 75 code frequency is supplied to the section in the rear, the equipment for the forward section will be automatically restored to its normal condition as soon as it is certain that energy has ceased to feed between the two sections.

Another object of the invention is to provide an improved system of thetype described which, after feeding of energ between a forward and a rearward section has been detected, operates to check the integrity of the insulated joints separating these sections and makes certain that energy is not feeding between these sectionsbefore the signal for thelforward section can be caused to display a permissive indication or energy of higher than 75 code frequency can be supplied to the rearwardsection.

Other objects of the invention and features of novelty will be apparent from the following description taken in connection with the accompanying drawing.

In-practicing our invention we provide a control relay for detecting the steadily energized condition of the trackrelay for the forward'section and employ this relay to control the associated wayside signal-and to also control the supply of steady energy to the rearward section. Should energy supplied to the rearward section feed to the track relay for the forward section, the control relay'releases to change the energy supplied to the rearward sectionfrom steady to 7-5 code frequency, and to hold'the associated wayside signal at stop. Should feeding of energy from the rearward to the-forward section cease so that the track relay for the forward section is operated-by 'unmutilated energy of or code frequencysupplied to the rails of the forward section at theexit end thereof and the 120 or 180 code detecting relay picks up, a circuit is established to pick up the control relay to establish the circuit for supplying steady energy to the rails of the rearward section. After this application of steady energy to the rails of the rearward section, the track relay for the forward section willnotrelease if energy-is feeding from the rearward to the forward section, and this system is arranged so that, if the track relay for the for-ward section does release, the equipment for the forward section is restored to its normal condition to permit clearing of the wayside signal for'the-section and to permit supply of coded energy of higher than '75 code frequency to the rearward section.

We shall describe one form of signaling system embodying our invention and shall then point out the novel features-thereof in claims.

In the drawing the single figure is a diagram of :a section of railway track equipped with signaling apparatus embodying our invention.

Referring to the drawing there is shown therein a stretch-of railway track having track rails l and 2 overwhich trafficnormally moves in the direction indicated by an arrow, that is, from left to right. The'rails of the track stretch are divided by insulated joints 3 into the customary successive track sections for signaling purposes.

Electric current is employed for propulsion purposes in the track stretch shown in the drawing and for this reason alternating current energy is employed in the track circuits, while impedance bonds 4 of the customary form are provided to conduct propulsion current around each pair of insulated rail joints. As the description proceeds, however, it will be apparent thatrthe apparatus of this invention is equally well suited for use on a steam road, in which either .direct or alternating current may be employedinthe track circuits while the impedance lbonds may be omitted.

In the drawing, one complete section, which is identified as section IZT, and parts of two other sections, identified as sections HT and I3T, are shown. Each of these sections has located at the entrance end thereof a signal S for governing traific in the track stretch. The signals illustrated are of the familiar color light type having an upper portion including a green lamp G, a yellow lamp Y, and a red lamp R, and a lower portion including a green lamp G and a red lamp R. It should be understood, however, that the invention is not limited to the use of signals of this type and that any appropriate form of signal may be used. Likewise, the invention is not limited to a system employing wayside signal-s, but is equally applicable to track stretches without wayside signals and over which are operated locomotives equipped with cab signal apparatus of well-known construction, such as that shown in Letters Patent of the United States No. 1,986,67 9, issued January 1, 1935, to Lloyd V. Lewis.

it assumes when the track stretch is vacant. At such times energy of 180 code frequency is supplied to the track transformer I2'I'I by the equipment associated with section I3T. The equipment for section I3T operates in the same manner as that for section MT.

The coded energy supplied to the transformer IZTT feeds to the track relay IZTR and produces code following operation of this relay. When the track relay contacts are in their picked-up positions, contact I6 establishes a circuit to supply energy to the first auxiliary relay IZFSA, while during the released periods of the track relay contacts energy is supplied to second auxiliary relay I ZBSA over the circuit which is traced from terminal B through back contact 16 of relay I2TR, front contact I! of relay l ZLOS, front contact ill of relay I2FSA, and winding of relay I2BSA to terminal C. At this time contact I8 of relay IZFSA also connects the snubbing resistor 20 across the terminals of the relay I2BSA to render the relay slow in releasing so that the -relay contacts remain picked up during the The rails of each track section form a part of a track circuit to which coded alternating current signal control energy is supplied at the exit or leaving end from the secondary winding of a track transformer TI. The alternating current supplied to the track circuits is derived from a suitable source and may be distributed throughout the track stretch by a transmission line, not shown. The terminals of the power supply source are designated BX and OK, and it will be assumed that the energy supplied from this source is alternating current of a frequency of 100 cycles per second.

Each signal location is also provided with a suitable source of direct current, such as a primary or storage battery, not shown, the terminals of which are designated B and C.

The signaling system shown in Fig. 1 makes use of track circuit energy coded at three different frequencies. This coded energy is provided by code transmitters CT which interrupt the supply circuits for the associated track transformers a definite number of times per minute accordingto traflie or other conditions ahead. As shown, each code transmitter is provided with three circuit making and breaking contacts 15, I20 and I80 which are continuously actuated by a motor or other suitable mechanism atspeeds such as to provide 75, 1 20 and 180 energy pulses per minute which are separated by periods of equal duration in which'no energy is supplied.

Each track circuit includes a code following track relay TR connected across the section rails at the entrance end of the section. As shown, the track relay is of the direct current type and is connected to the track rails through a resonant rectifier unit RU, which includes a transformer, a capacitor and a reactor so arranged and proportioned as to freely pass 100 cycle signal control energy, but so as not to pass propulsion current of a different frequency. The unit RU includes, in addition, a rectifier which converts into direct current the alternating current supplied through the unit.

The track relay IZTR has associated therewith auxiliary relays IZFSA, IZBSA, IZH, iZJ and 12K, a slow releasing control relay IZLOS, and a decoding transformer I ZDT, while each of the other signal in the track stretch has associated therewith equipment corresponding to that as.- sociated with signal I2S.

The equipment is shown in the condition which picked-up periods of the track relay contacts. Similarly, the relay IZFSA is of a type the contacts of which are slow in releasing so that they remain picked up during the released periods of the track relay contacts. 1

As a result of code following operation of the track relay its contact 2| alternately establishes the circuits to energize the two portions of the primary winding of transformer IZDT so that impulses of energy are supplied to the secondary windings 22 and 23 of the transformer.

When the track relay contacts are picked up, its contact 25 establishes a circuit including front contact 26 of relay IZBSA to supply impulses of energy from the transformer secondary winding 23 to the relay NH. The relay H is of a type which is slow in releasing so that its contacts remain picked up during the intervals between the supply of impulses of energy to the relay winding.

As the track relay is operated by energy of 180 code frequency, energy is supplied through the resonant rectifier unit IDU to the relay NJ and itscontacts are picked up.

As the contacts of relays IZFSA and IZBSA are picked up, energy is supplied to the control relay I2LOS over the circuit which includes front contact 28 of relay I2FSA and front contact 29 of relay IZBSA, while energy is also supplied to relay IZLOS over front contact 40 of relay IZJ.

As the contacts of relays IZFSA, IZBSA, 12H and I2J are picked up, energy of code frequency is supplied to the primary winding of track transformer IITT over the circuit which is traced from terminal BX through contact I80 of the code transmitter I2CT, front contact 42 of relay I2J, back contact ll of relay IIK, front contact 30 of relay IZH, front contact 3| of relay IZBSA, front contact 32 of relay IZFSA, and primary winding of transformer HT to terminal CX. Accordingly, energy of 180 code frequency is supplied to the rails of section HT.

As relays IZH and [2.7 are picked up, energy is supplied over front contact 34 of relay IZH, and front contact 35 of relay IZJ to the green lamp G of the upper portion of signal 128, while energy is supplied over front contact 45 of relay 12H and front contact 46 of relay |2J to the red lamp R of the lower portion of signal IZS with the result that the signal displays its clear indication comprising a green over a red lamp.

Operation of equipment on passage of a train through the track stretch leased positions so that energy is not supplied to the relays I ZFSA, I2H and 'I2J. Accordingly, after a short time interval the contacts of relay IZFSA release so that its contact l8 interrupts both the energizing circuit and the snubbing circuit for relay I2BSA, and the contacts of this relay thereupon quickly release so that contact 26 interrupts the circuit of relay IZI-l and its contacts release after a time interval.

On release of the contacts of relay IZFSA contact 28 interrupts the circuit of relay IZLOS, "but this relay is slow enough in releasing to remain picked up until contact '29 of relay IZBSA releases and establishes the circuit of the relay IZLOS. Accordingly, the contacts of relay IZ-LOS remain picked up and energy of 75 code frequency is supplied to the track transformer HTT over the circuit which is traced from terminal BX through front contact 31 of relay IZLOS, back contact 3| of relay IZBSA, back contact 32 of relay IZFSA, contact I5 of the code transmitter, and primary winding of the track transformer I ITT to terminal CX.

As hereinafter explained in connection with section IZT, the energy of 75 code frequency supplied to section I IT will cause the signal for that section to display a yellow over a red indication, while it Will produce a similar aspect in the cab signal apparatus on a locomotive in section T.

On release of the contacts of relay I2H contact 34 interrupts the circuit of the greenlamp'G'and establishes the circuit of the red lamp R of the upper portion of signal IZS, while contact 45 of relay IZH interrupts one circuit for lighting the red lamp R of the lower portion of signal 128 and establishes another circuit for this lamp so the signal IZS displays its stop indication comprising a red lamp over a red lamp. On cessation of code following operation of the track relay IZTR, relay I 2J releases and its contact Ml interrupts the circuit which it controls for energizing relay IZLOS.

When the train enters section IST, the equipment for thissection operates in the same manner as that associated with section I-2T so that the signal ISS displays its stop indication, while the energy supplied to track transformer IZTT is changed fro-m 180 to 75 code frequency.

When the train v'acates section I'ZT, the energy of '7 5 code frequency feeds to the track relay 'IZTR. and produces code following operation of the relay. 7

On picking up of the track relay IZTR, its'contact IE establishes the circuit to supply energy to relay iZFSA and the contacts of this relay pick up so that contact 32 interrupts the circuit traced above for supplying energy of 75 code frequency to the transformer IITT, and establishes the circuit including front contact 31 of relay [BIOS and back contact 3| of relay "IZBSA over which steady uncoded energy may be supplied to transformer IITT. If the insulated joints 3 separating sections IlTand I2T are intact, the energy supplied to track transformer I ITT will not reach track relay IZTR and this relay will continue to respond to'the coded-energy supplied thereto from transformer I2TT.

After a short time interval, therefore, the'track relay contacts will release and contact; establishes the circuit including front contact 1-"! of relay IZLOS and front contact 18 of relay I'2FSA for energizing relay IZBSA. The contacts of relay IZBSA, therefore, pick up and its contact 26 is closed so that on the next movement of the track relay contacts to their picked-up positions energy is supplied to relay IZI-I, while contact 3| of relay IZBSA interrupts the circuit traced above for supplying steady energy to track transformer 'I ITT.

In addition, on picking up of the contacts of relay I2BSA its contact 29 establishes the circuit including front contact 28 of relay I2FSA for supplying energy to the relay IZLOS. In the interval between picking up of the contacts of relay I2FSA and picking up of the contacts of relay IZBSA energy is not supplied to the relay I2LOS, but this relay is slow enough in releasing to keep its contacts picked up during this time interval.

When the track relay contacts again pick up, energy is supplied to relay I2FSA to keep it picked up, while energy is supplied to relay 'IZI-I to pick up its contacts. On picking up of the contacts of relay 12H, its contact 30 completes the circuit including 'back contact AI of relay I2K and back contact 42 of relay IZJ for supplying energy of code frequency to track transformer IITT, while its contact 34 interrupts the circuit of the red lamp R and establishes the circuit including back contact 35 of relay I2J for lighting the yellow lamp Y of the upper portion 'of signal IZS. At this time, contact 45 of relay 'I'2H interrupts one circuit for the red lamp R of the lower portion of signal 128 and establishes the circuit including back contact 46 of relay I2J and back contact 41 of relay IZK forlighting this lamp and this signal displays its approach indication comprising a yellow lamp over a red lamp. As hereinafter explained, the energy of 120 code frequency supplied to the rails of section IIT causes the signal for that section to display its approach medium indication consisting of a yellow over a green lamp, While it will cause the display of a similar indication by the cab signal apparatus on a locomotive present in this section.

On continued code following operation of the track relay I2TR energy is supplied to the relays IZFSA and l2I-l on movement of the track relay contacts to their picked-up positions, while ene'rgy is supplied to the relay IZBSA on movement of the track relay contacts to their released positions. Accordingly, as long as the track relay responds to coded energy, the contacts of the relays IZFSA, IZBSA and IZH are picked up, while contact 28 of relay I ZFSA and contact 29 of relay I2BSA establish the circuit of the relay IZLOS so that its contacts-are maintained picked up.

At this time, as the track relay IZTR is respending to energy of. '75 code frequency, the frequency of the energy induced in the secondary winding 22 of decoding transformer I ZDT is such that too little energy is supplied through the units IZBDU and IBUDU to the relays IZK and NJ to pick up the contacts of these relays and they remain released.

When the train advances far enough to vacate section IST, the equipment associated with this section operates to change the aspect of signal 133 from red over red to yellow over red, and to change the-energy supplied to track transformer HTT from '75 to 120 code frequency. Accordingly, the track relay 12TH operates at a faster rate andrelays IZFSA, I ZBSA and IZH are maintained energized, while sufiicient energy is supplied through the unit 'IZfiDU to the relay [2K to pick upthe relay contacts 'so that its contact 4! interrupts the circuit of the red 'lampR and establishes the circuit of the green lamp G of the lower portion of signal I 28 so this signal displays its advance approach indication comprising a yellow lamp over a green lamp.

On picking up of relay I2K its contact 4| changes the energy supplied to track transformer IITT from 120 to 180 code frequency, while contact 48 of relay IZK establishes a circuit for supplying energy to relay IZLOS.

When the section in advance of section I3T is vacated, energy of 120 code frequency is supplied over the section rails so the equipment for section I 3T operates to supply energy of 180 code frequency to track transformer I2T'I' and on resultant operation of track relay IZ'I'R at the 180 code rate relay I2J picks up and relay I2K releases and the equipment assumes its originally described condition in which energy of 180 code frequency is supplied to the track transformer IITT, and the signal IZS displays its clear indication comprising a green over a red lamp.

Operation of the equipment if an insulated :ioint breaks down as a result of passage of a train When a train moving in the normal direction of traffic enters section IZT, the track relay IZTR is shunted and relays IZFSA, IZBSA, [2H and I2J or IZK release as explained above, while energy is supplied to relay IZLOS over the circuit established by back contacts 28 and 29 of relays IZFSA and IZBSA. Accordingly, the circuit including front contact 31 of relay IZLOS, back contact 3| of relay IZBSA, back contact 32 of relay IZFSA, and contact 15 of the code transmitter I2C'I is established to supply coded energy to the transformer II'I'I.

For purposes of illustration it will be assumed that an insulated joint 3 separating sections HT and IZT breaks down as a result of passage of a train. Because of the well-known autotransformer action of the impedance bonds, breaking down of one insulated joint permits energy supplied to the rails of section IIT to feed to the track relay IZTR.

Accordingly, when the train advances far enough for the rear of the train to be located some distance in advance of the entrance end of the track section 1 2T so that the train is ineffective to shunt the track relay IZTR with respect to energy feeding across the defective joint, the track relay IZTR, will respond to energy supplied from transformer H'I'T.

On the first movement of the track relay contacts to their picked-up positions contact [6 establishes the circuit to supply energy to the relay I2FSA, and the contacts of this relay pick up so that its contact 32 interrupts the circuit traced above for supplying energy of '75 code frequency to track transformer iITT and establishes the circuit including front contact 3! of relay IZLOS and back contact 3| of relay I'2BSA for supplying steady energy to the transformer l ITT. This steady energy feeds across the defective joint to the track relay IZTR and keeps the contacts of this relay in their picked-up positions so that contact I6 maintains the supply of energy to relay IZFSA, and does not engage its back contact to establish the circuit to supply energy to the relay I2BSA. Accordingly, the contacts of relay IZBSA remain released.

When the contacts of relay IZFSA are picked up and the contacts of relay IZBSA are released, the circuit governed by these relays for energizing the relay IZLOS is interrupted, and at this time the circuits governed by contact 40 of relay I2J and contact 48 of relay [2K for supplying energy to relay IZLOS are also interrupted and, after a short time interval, the contacts of relay IZLOS release so that its contact 31 interrupts the circuit traced above for supplying steady energy to the track transformer I l'l'I' and establishes a circuit including contact 15 of the code transmitter to supply energy of 75 code frequency to the track transformer HTI. In addition, on release of the contacts of relay IZLOS its contact I! interrupts the circuit of relay IZBSA to prevent energization of this relay.

The coded energy supplied to track transformer IITT feeds to the track relay IZTR and the contacts of this relay now follow code. However, on release of the track relay contacts energy is not supplied to relay |2BSA since the circuit of this relay is interrupted by contact ll of relay I2LOS and relay IZBSA remains released so that its contact 26 interrupts the circuit of the relay l 2H to thereby prevent the supply of energy to relay |2H on movement of the track relay contacts to their picked-up positions. Furthermore, as relay I2TR i being operated by energy of 75 code frequency the relays I2J and MK remain released and do not establish circuits to energize relay IZLOS. Accordingly, on continued code following operation of the track relay IZTR subsequent to release of relay I 2LOS energy is supplied to relay l2FSA on movement of the track relay contacts to their pick-up positions, while energy is not supplied to relays I 2BSA, IZH, 12K and I2J so that relay IZBSA remains released and continues to interrupt the circuit of relay IZLOS, and relay |2H remains released and it contacts 34 and maintain the circuits of the red lamps R of signal IZS.

It will be seen, therefore, that this system is arranged so that on initial picking up of the track relay contacts steady energy is supplied to 40 the section in the rear, and, if this steady energy feeds across a defective joint, it will keep the track relay picked up so that the relay LOS releases and cuts off the supply of steady energy to the section in the rear and causes coded energy of 75 code frequency to be supplied thereto. As hereinafter explained, this energy of 75 code frequency supplied to section IIT causes the signal for that section to provide its approach indication, while it will produce a similar indication by the cab signal apparatus on a locomotive present in that section. In addition, release of relay IZLOS prevents completion of the cycle of picking up of the auxiliary relays and thereby insures that the signal IZS controlled thereby will continue to display its stop indication.

This system is also arranged so that the equipment associated with the track section in the rear of a defective insulated joint will display its approach indication.

For the purposes of illustration it will be assumed that an insulated joint 3 separating sections I 2T and HT breaks down as a result of passage of a train and that the equipment for section [3T operates as described in detail above in connection with section IZT to detect the defective condition of the insulated joints.

As explained above, when any part of the train is present in section I2T, current from the track transformer I2TT is shunted from the track relay I2I'R, while when the train enters section I3T, the track relay for that section is shunted and the equipment controlled thereby operates to supply energy of 75 code frequency to the track transformer I2TT.

I When the train vacates section I2T, the energy of '75 code frequency supplied to transformer IZTT feeds to the track relay IZTR and the first impulse of coded energy pick up the contacts of this relay so that its contact ['6 establishes the circuit of the relay IZFSA, while on the first off period in the code the track relay contacts release so that energy is supplied to relay IZBSA and contact 29 of this relay picks up and reestablishes the circuit of the relay IZLOS.

When the train advances far enough for the rear of the train to be located some distance inadvance of the entrance end of section I3T, the train is no longer effective to shunt the track relay for section I3T with respect to energy feeding from the track transformer IZTT across the defective joint.

On the first movement of the contacts of the track relay for section I3T to their picked-up position energy is supplied to the relay I3FSA,

.not shown, and its contacts pick up to cut off the supply of coded energy to transformer IZTT and to cause steady energy to be supplied thereto. In addition, on picking up of the contacts of relay I3FSA the circuit of relay I3LOS' is interrupted and the release time of this relay begins.

The steady energy supplied to the transformer I2TT causes. the contacts of track relays IZTR and I3TR to remain picked up and maintain the circuits of the associated relays FSA.

After a time interval the relay I3LOS releases and cuts off the supply of steady energy to transformer IZTT and causes coded energy to be supplied thereto, While it also interrupts the circuit of relay LSBSA to prevent energization of this relay on subsequent code following operation of the track relay I3TR.

On the supply of steady energy to relay IZTR. its contacts remain picked up so that energy is not supplied to relay IZBSA and this relay releases after a time interval. This period is relatively long as the snubbing circuit for the relay is maintained by contact 18 of relay IZ FS-A. Un-

til relay I2BSA releases energy is supplied torelay I2LOS so that the release period of this relay lZLOS does not begin until after release of relay I2BSA. As pointed out above, the release period of relay I3LOS begins as soon as relay I3FSA picks up. As a result, the relay IZLOS will remain picked up and will maintain the circuit of the relay I2BSA until after the relay I3LOS releases and causes coded energy to be supplied to transformer I2TT. Accordingly, on the first off interval in the coded energy supplied after release of the contacts of relay I3LOS, the contacts of relay IZTR release and energy is supplied to relay ILZBSA to pick up the relay contacts if they have released, or to maintain them picked up if they have not released. The contacts of relay lZBSA, therefore, either maintain the circuit of relay IZLOS or reestablish it before it has been interrupted long enough for the relay I2LO-S to, have become released and interrupt the circuit of the relay IZBSA.

On continued supply of coded energy to the relay I2TR, therefore, on movement of the track relay contacts to their picked-up. positions energy is supplied to relay IZFSA and is also supplied from the transformer IZDT to relay IZH, while on movement of the track contacts to their released positions energy is supplied to relay IZBSA.

As relays IZFSA, IZBSA and IZH are picked up, energy of 120 code frequency is supplied to transformer HTT, while as relay 12H is picked up, its contact 34 establishes the circuit of the 10 yellow lamp Y of the upper portion of signal I28 and its contact 45 establishes a circuit for supplying energy to the red lamp R of-the lower portion of signal l 25.

On the supply of coded energy to relay i3TR subsequent to release of relay I3LOS this track relay follows code and during the picked-up periods of its contacts energy is supplied to the relay IBFSA, but during the released periods ofthe track relay energy is not supplied to relay I3BSA as the circuit of this relay is interrupted by relay I3LOS. Accordingly, relay |3BSA will interrupt the circuit of relay 131-1 and this relay will maintain the circuit of the red lamp of si nal 13S.

From the foregoing it will be seen that when an insulated joint separating two sections breaks down as a result of passage of a train, this system operates to supply steady energy to the section in the rear to test the joints, but after a short period the supply of steady energy is cut off and coded energy is again supplied, and this coded energy causes the display of the approach indication by the signal for the section in the rear of the defective joints, or by the cab signal apparatus on a locomotive present in that section.

Operation of equipment if an insulated joint breaks down when the track stretch is vacant For purposes of illustration it will be assumed that one of the joints separating sections HT and IZT breaks down at a time when the track stretch is vacant. As the stretch is assumed to be vacant, energy of code frequency is supplied to transformer I2TT, while all of the auxiliary relays except relay IZK associated with track relay IZTR are picked up so that signal 12S displaysits green or clear indication and energy of 180 code frequency is supplied to the transformer HTT.

If at the time the insulated joint separating sections HT and I2T breaks down the impulses of energy supplied to section III are out of step with those supplied to section I2T, the impulses of energy supplied to section HT and feeding over the defective insulated joint to track relay I2TR will fill in the off periods in the code supplied to section IZT so that the track relay IZTR will be maintained picked up all, or substantially all, of the time.

If, at the time the insulated joint becomes defective, the impulses of code supplied to the two sections are substantially in step with each other, they will soon become out of step. This will be true because the code transmitters which create the code for the two sections are driven by electric motors of the squirrel cage induction type, and these motors will not operate at exactly the same speed for any substantial period of time. Accordingly, if track relay tZTR is not heldpicked up an abnormally large proportion of the time immediately upon breaking down of the joint, the track relay will soon be held up an abnormal ly large proportion of the time because of the increase in the time during which energy is supplied to the track relay when the two codes get out of step.

In consequence of the lengthened picked-up periods of track relay IZTR contact [6 will not engage its back contact, or will engage it for such short time intervals that energization of relay LZBSA is reduced below the value effective to maintain the relay picked up and the relay contacts release. As the track relay is maintained picked up most of the time,energy is supplied to the relay IZFSA to maintain it picked up.

On release of relay IZBSA its contact 3| interrupts the circuit for supplying energy of 180 code frequency to the transformer IITT and establishes the circuit including front contact 31 of relay I ZLOS, back contact 3I of relay IZBSA, and front contact 32 of relay IZESA for supplying steady energy to transformer I ITT. In addition, on release of relay IZBSA its contact 29 interrupts the circuit of relay IZLOS and the release period of this relay begins.

Furthermore, on release of relay I2BSA its contact 26 interrupts the circuit of relay I2I-I so that it releases and causes signal I2S to display its stop indication.

The steady energy supplied to transformer I ITT feeds across the defective joint to relay IZTR so that this relay is maintained constantly picked up to thereby maintain the circuit of relay I2FSA and to prevent the supply of energy to relay IZBSA. As the track relay I2TR is steadily energized current is not supplied to relay I2J and it releases, if it has not already released due to the lengthened picked-up periods of the track relay, and contact 40 of relay I2J interrupts the circuit which it controls for supplying energy to relay IZLOS. After ashort time interval, relay I2LOS releases and interrupts the circuit of relay IZBSA, while it also cuts off the supply of steady energy to section HT and causes energy of '75 code frequency to be supplied thereto. This energy feeds across the defective joint to relay IZ'I'R and combines with the energy of 1830 code frequency supplied from transformer I2TT so that track relay IZTR is maintained picked up most of the time and energy, therefore, is supplied to relay IZFSA to keep it picked up and thus keep relay I2LOS released. Even if th contacts of the track relay release at times, energy will not be supplied to relay IZBSA as the circuit of this relay is interrupted by contact I! of relay IZLOS. Relay IZBSA, therefore, will remain released and .will prevent energization of relay IZH so that the signal I2S will continue to display its stop'indication. The relays I 2K and IN will not pick up in response to energy supplied from the decodin transformer IZDT during irregular operation of the track relay I2TR by energy of both 75 and 180 code frequency. Accordingly, relays I2J and 'IZK remain released'and do not establish circuits for supplying energy to relay IZLOS.

On release of relay IZBSA and the supply of steady energy to section HT the track relay for this section is held picked up, but as explained above, the relay I ILOS associated therewith does not start to release until after relays IIBSA and IIJ release, while the release time of relays IIBSA and I IJ does not start until after relay I 2BSA releases and initiates the supply of steady energy to section HT, and the relay IILOS is certain to remain picked up until after relay I2LOS releases and causes coded energy to again be supplied to section HT. This coded energy of 75 code frequency will cause the signal for section IIT to display its approach indication.

Restoring equipment to normal operation after a defective joint has been detected The system of this invention is arranged so that after the equipment for a section detects the presence of a defective joint, and the joint 12 has been repaired, the equipment may be restored to normal operation by interrupting the circuit of the relay FSA by means provided for this purpose. a

As previously explained, after a defective joint has beendetected, relay FSA is energized while relays BSA and LOS are deenergized. As relay LOS is deenergized, it interrupts the circuit of relay BSA, and as relay BSA is deenergized and FSA is energized, the circuit of relay LOS is interrupted. Accordingly, as long as the track relay follows coded energy, relay FSA will be maintained picked up while relays BSA and LOS will remain released. This will be true even after the defective joint is repaired so that the track relay is no longer supplied with energy feeding across the defective joint.

In order to restore the equipment to normal operation the signal maintainer or other authorized person depresses the push button I2PB and thus interrupts the circuit of relay I2FSA so that it releases and its contact 28 establishes the circuit of relay IZLOS. Relay I2LOS thereupon picks up and establishes the circuit of relay IZBSA. After the push button is released and restores the circuit of relay FSA, this relay picks up on the first movement of the track relay contacts to their picked-up position, while the equipment thereafter functions in the normal manner.

This system is also arranged so that it automatically resumes normal operation when feeding of energy between sections ceases and the track stretch is vacant.

As just explained, when a joint is defective, relay IZFSA is picked up and relays I2BSA, I2H, I2LOS, IZK and I2J are released. As long as energy feeds from section HT to track relay I ZTR, the relay I 2FSA is held picked up and the other relays remain released. If feeding of energy from section HT to track relay I2TR ceases so that the track relay is operated solely by energy of or code frequency supplied to the rails of section I2T at the exit end thereof, energy will be supplied from the decoding transformer I2DT to pick up relay IZK or I 2J so that one of these relays establishes a circuit for relay I2LOS and its contacts pick up.

When relay IZLOS picks up, its contact 31 interrupts the circuit for supplying energy of 75 code frequency to the transformer IITT and establishes the circuit including back contact 3| of relay IZBSA and front contact 32 of relay IZFSA over which steady energy may be supplied to the transformer IITT. The energy supplied to section IIT at this time checks the integrity of the insulated joints and makes certain that energy supplied to section I IT does not reach track relay I2TR because if ener y supplied to transformer IITT does feed to track relay I2TR, the relay contacts will remain picked up to interrupt the circuit of relay IZBSA while energy will no longer be supplied from the decoding transformer IZDT to relays IZJ and I2K and Whichever one of these was picked up will T818850 If, at the time relay I2LOS picks up and establishes the circuit over which steady energy may be supplied to transformer HTT, the insulated joints separating sections I IT and I2T are intact and energy supplied to section I IT does not reach relay IZTR, this relay will continue code following operation and energy will be supplied over back contact I6 of the track relay IZ'I'R, front contact I I of relay I2LOS, and front contact I8 of relay I2FSA to relay I ZBSA and its contacts pick up to establish the circuit of relay IZH and 13; on continued operation of the track relay the, relay I2H picks up and relays IZFSA, IZBSA, |-2'LOS, and I2J or I2K remain picked up to cause Signal l-ZS to display an appropriate permissive indication and to cause energy of 180 code frequency to be supplied to the rails of section HT.

As this system operates to automatically restore normal operation of the equipment when. feeding of energy between sections ceases, it eliminates traffic delays which might otherwise occur after temporary feeding of energy between sections. As this system operates to check that energy does not feed between sections before it permits normal operation of the equipment to be resumed, there is no possibility that normal operation of the equipment will be resumed unless it is proper.

Although We have illustrated and described only one form of railway signaling system embodying our invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of our invention.

Having thus described our invention, what we claim is:

1. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into a plurality of successive track sections including a forward and a rearward section, means for at times supplying energy of a first code frequency and at other times supplying energy of a second code frequency to the rails of said forward section, a code following track relay having a winding receiving energy over the rails of said forward section, a control relay having contacts movable between a first and a second position, means for supplying energy of said first code frequency to the rails of said rearward section when the contacts of said track relay are steadily released or the contacts of said control relay are in their second position, means responsive to operation of the track relay contacts following a period in which the track relay has not been responding to coded energy to establish a circuit including a first position contact of said control relay over which steady energy may be supplied to the rails of said rearward section, means responsive to code following operation of said track relay subsequent to establishment of said circuit over which steady energy may be supplied to the rails of said rearward section provided the contacts of said control relay are in their first position for interrupting the circuit over which steady energy may be supplied to the rails of said rearward section and for supplying energy of said second code frequency to the rails of said rearward section, means responsive to code following operation of said track rela for maintaining the contacts of said control relay in their first position provided they are in such position but ineffective to cause the contacts of said control relay to move from their second to their first position, means for moving the contacts of said control relay from their first to their second position when the contacts of said track relay remain continuously picked up for a predetermined time interval or are picked up for an abnormally large proportion of the time for a substantial interval, an auxiliary relay responsive only to operation of said track relay by energy of said second code frequency, and means governed by said auxiliary relay for causing the contacts of said control relay to occupy their first position.

2. In a coded railway signaling system, in combination, a stretch of railway track having a pairof track rails divided by insulated joints into a plurality of successive track sections including a forward and a rearward section, means for at times supplying energy of a first code frequency and at other times supplying energy of a second code frequency to the rails of said forward section, a code following track relay having a winding receiving energy over the rails of said forward section, a slow release control relay, means for supplying energy of said first code frequency to the rails of said rearward section when the contacts of said track relay are steadily released or the contacts, of said control relay are released, meansv effective on picking up of the track relay contacts following a period in which the track relay has not been responding to coded energy or when the track relay contacts are picked up an abnormally large proportion of the time to establish a supply circuit including a front contact of said control relay over which steady energy. may be supplied to the rails of said rearward section, means responsive to code following op.- eration of said track relay subsequent to establishment of said supply circuit provided the contacts of said control relay are picked up for interrupting said supply circuit and for supplying energy of said second code frequency to the rails of said rearward section, means governed by said track relay for supplying energy to said control relay only when the contacts of said control relay are picked up, said means being. effective to cause energy to be supplied to said control relay when said track relay is responding to coded energy and being ineffective to cause energy to be supplied to said control relay when the contacts of said track relay are continuously picked up for a predetermined time interval or are picked up for an abnormally large proportion of the timefor a substantial interval, an auxiliary relay responsive only to operation of said track relay by energy of said second code frequency, and a circuit governed by said auxiliary relay for picking up the contacts of said control relay.

3. In a coded railway signaling system, in combination, a stretch of railway track having a pair. of track rails divided by insulated joints into a plurality of successive track sections including a forward and a rearward section, means for at.

times supplying energy of a first code frequency and at other times supplying energy of a second code frequency to the rails of said forward section, a code following track relay having a winding receiving energy over the rails of said forward section, a signal for said forward section capable of displaying a stop indication and at least one permissive indication, a control relay having contacts movable between a first and a second position, means for supplying energy of said first code frequency to the rails of said rearward section when the contacts of said track relay are steadily released or the contacts of said control relay are, in their second position, means effective on picking up of the track relay contacts following a period in which the track relay has not been responding to coded energy or when the track relay contacts are picked up an abnormally large proportion of the time to establish a supply circuit including a first position contact of said control relay over which steady energy may be supplied to the rails of said rearward section, means responsive to code following operation of said track relay subsequent to establishment of said supply circuit provided the contacts of said control relay are in their first position for interrupting said supply circuit and for supplying energy of said second code frequency to the rails of said rearward section, means responsive to code following operation of said track relay for maintaining the contacts of said control relay in their first position provided they are in such position but ineffective to cause the contacts of said control relay to move from their second to their first position, means for moving the contacts of said control relay from their first to their second position when the contacts of said track relay remain continuously picked up for a predetermined time interval or are picked up for an abnormally large proportion of the time for a substantial time interval, an auxiliary relay responsive only to operation of said track relay by energy of said second code frequency, a circuit governed by a contact of said auxiliary relay for causing the contacts of said control relay to occupy'their first position, and means responsive to code following operation f d tra k relay for causing said signal to display a, permissive indication provided the contacts of said control relay are in their first position.

4'. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into a plurality of successive track sections including a forward and a rearward section, means for at times supplying energy of a first code frequency and at other times supplying energy of a second code frequency to the rails of said forward section, a code following track relay having a winding receiving energy over the rails of said forward section, a first and a second auxiliary relay, a slow releasing control relay, a circuit including a back contact of said first auxiliary relay for supplying energy to said control relay, a circuit including a front contact of said second auxiliary relay for also supplying energy to said control relay, a circuit including a front contact of the track relay for supplying energy to the first auxiliary relay, a circuit including a back contact of the track relay and front contacts of said first auxiliary relay and of said control relay for supplying energy to said second auxiliary relay, a circuit including a back contact of one of said auxiliary relays for supplying energy of said first code frequency to the rails of said rearward section, a circuit including front contacts of said first auxiliary relay and of said control relay and a back contact of the second auxiliary relay over which steady energy may be supplied to the rails of said rearward section, means responsive to code following operation of said track relay provided the contacts of said second auxiliary relay are picked up for supplying energy of said second code frequency to the rails of said rearward section, a third auxiliary relay responsive only to operation of said track relay by energy of said second code frequency, and a circuit governed by a contact of said third auxiliary relay for supplying energy to said control relay.

5. In a coded railway signaling system, in com.. bination, a stretch of railway track divided by insulated joints into a plurality of successive track sections including a forward and a rearward section, means for at times supplying energy of a first code frequency and at other times supplying energy of a second code fre-.

quency to the rails of said forward section, a code following track relay having a winding receiving energy over the rails of said forward section, a control relay having contacts movable between a first and a second position, a circuit 16 including a front contact of said track relay for supplying energy to a first auxiliary relay, a circuit including a back contact of said track relay. a front contact of said first auxiliary relay and a first position contact of said control relay for supplying energy to a second auxiliary relay, a circuit including a back contact of one of said auxiliary relays for supplying energy of said first code frequency to the rails of said rearward section, a circuit including a front contact of said first auxiliary relay, a back contact of said second auxiliary relay and a first position contact of said control relay over which steady energy may be supplied to the rails of said rearward section, means responsive to code following operation ofsaid track relay provided said second auxiliary relay is picked up forsupplying energy of said second code frequency to the rails of said rearward section, means for causing the contacts of said control relay to occupy their first position until the contacts of said first and second auxiliary relays have been out of correspondence for a predetermined time interval, a third auxiliary relay responsive only to operation of said track relay b energy of said second code frequency, and a circuit governed by a contact of said third auxiliary relay for causing said control relay contacts to occupy their first position.

6. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into a plurality of successive track sections including a forward and a rearward section, means for at times supplying energy of a first code frequency and at other times supplying energy of a second code frequency to the rails of said forward section, a code following track relay having a winding receiving energy over the rails of said forward section, a signal for said forward section capable of displaying a stop indication and at least one permissive indication, a slow release control relay, means for supplying energy of said first code frequency to the rails of said rearward section when the contacts of said track relay are steadily released or the contacts of said control relay are released, means effective on picking up of the track relay contacts following a period in which the track relay has not been responding to coded energy or when the track relay contacts are picked up an abnormally large proportion of the time to establish a supply circuit including a front contact of said control relay over which steady energy may be supplied to the rails of said rearward section, means responsive to code following operation of said track relay subsequent to establishment of said supply circuit provided the contacts of said control relay are picked up for interrupting said supply circuit and for supplying energy of said second .code frequency to the rails of said rearward section, means governed by said track relay for supplying energy to said control relay only when the contacts of said control relay are picked up, said means being effective to cause energy to be supplied to said control relay when said track relay is responding to coded energy and being ineffective to cause energy to be supplied to said control relay when the contacts of said track relay are continuously picked up for a predetermined time interval or are picked up for an abnormally large proportion of the time for a substantial interval, an auxiliary relay responsive to operation of said track relay only by energy of said second code frequency, a circuit governed by said auxiliary relay for picking up the contacts of said control relay, and means responsive to code following operation of said track relay for causing said signal to displa a permissive indication provided the contacts of said control relay are picked up.

7. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into a plurality of successive track sections including a forward and a rearward section, means for at times supplying energy of a first code frequency and at other times supplying energy of a second code frequency to the rails of said forward section, a code following track relay having a winding receiving energy over the rails of said forward section, a control relay having contacts movable between a first and a second position, means for supplying energy of said first code frequency to the rails of said rearward section when the contacts of said track relay are steadily released or the contacts of said control relay are in their second position, means responsive to operation of the track relay contacts following a period in which they have been steadily released to establish a supply circuit over which steady energy may be sup-plied to the rails of said rearward section, means responsive to code following operation of said track relay subsequent to establishment of said supply circuit provided the contacts of said control relay are in their first position for interrupting said supply circuit and for supplying energy of said second code frequency to the rails of said rearward section, means responsive to code following operation of said track rela for maintaining the contacts of said control relay in their first position provided they are in such position but ineffective to cause the contacts of said control relay to move from their second to their first position, means for moving the contacts of said control relay from their first to their second position when the contacts of said track relay remain continuously picked up or are picked up for an abnormally large proportion of the time for a substantial time interval, an auxiliary relay responsive only to operation of said track relay by energy of said second code frequency, and a circuit governed by said auxiliary relay for causing the contacts of said control relay to occupy their first position.

8. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into a plurality of uccessive track sections including a forward and a rearward section, means for at times supplying energy of a first code frequency and at other times supplying energy of a second code frequency to the rails of said forward section, a code following track relay having a winding receiving energy over the rails of said forward section, a slow release control relay, a circuit including a front contact of said track relay for supplying energy to a first auxiliary relay, a circuit including a back contact of said track relay and front contacts of said first auxiliary relay and of said control relay for supplying energy to a second auxiliary relay, means responsive to code following operation of said track relay provided the contacts of said second auxiliary relay are picked up to supply energy to a third auxiliary relay, a circuit including back contacts of said first and second auxiliary relays and a front contact of said control relay for supplying energy of said first code frequency to the rails of said rearward section, a circuit including front contacts of said first auxiliary relay and of said control relay and a back contact of said second auxiliary relay over which steady energy may be supplied to the rails of said rearward section, a circuit including front contacts of said first, second and third auxiliary relays for supplying energy of said second code frequency to the rails of said rearward section, a circuit including a back contact of said first auxiliary relay for supplying energy to said control relay, a circuit including a front contact of said second auxiliary relay for supplying energy to said control relay, a fourth auxiliary relay responsive only to operation of said track relay by energy of said second code frequency, and a. circuit governed by said fourth auxiliary relay for supplying energy to said control relay.

9. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into a plurality of successive track sections including a forward and a rearward section, means for at times supplying ener y of a first code frequency and at other times supplying energy of a second code frequency to the rails of said forward section, a code following track relay having a winding receiving energy over the rails of said forward section, a, signal for said forward section capable of displaying a stop indication and at least one permissive indication, a slow release control relay, a circuit including a front contact of said track relay for supplying energy to a first auxiliary relay, a circuit including a back contact of said track relay and front contacts of said first auxiliary relay and of said control relay for supplying energy to a second auxiliary relay, means responsive to code following operation of said track relay provided the contacts of said second auxiliary relay are picked up for supplying energy to a third auxiliary relay, a circuit including back contacts of said first and second auxiliary relays and a front contact of said control relay for supplying energy of said first code frequency to the rails of said rearward section, a circuit including front contacts of said first auxiliary relay and of said control relay and a back contact of said second auxiliary relay over which steady energy may be supplied to the rails of said rearward section, a circuit including front contacts of said first, second and third auxiliary relays for supplying energy of said second code frequency to the rails of said rearward section, a circuit including a back contact of said first auxiliary relay for supplying energy to said control relay, a circuit including a front contact of said second auxiliary relay for supplying energy to said control relay, a fourth auxiliary relay responsive only to operation of said track relay by energy of said second code frequency, a circuit governed by said fourth auxiliary relay for supplying energy to said control relay, and means for causing said signal to display its stop indication or a permissive indication according as the contacts of said third auxiliary relay are released or are picked up.

RALPH R. KEMMERER. ARTHUR L. JEROME.

REFERENCES CITED The following references are of record in th file of this patent:

UNITED STATES PATENTS Number Name Date 2,235,134 Allison et al Mar. 18, 1941 2,357,236 Thompson Aug. 29, 1944 

